Mobile radio-utilizing device

ABSTRACT

A current restriction structure for restricting a higher-harmonic-wave current generated in a digital circuit block from entering a radio circuit block and/or a radio-frequency current generated in the radio circuit block from entering the digital circuit block is disposed between the radio circuit block and the digital circuit block. The current restriction structure is formed by one or two of equivalent rectangular cylindrical metallic tube including metallic planes overlying/underlying the ground layer and a narrow-pitch via-hole array, which are disposed to enclose the subject current to be restricted and have a short-circuited distal end. The distance between the open plane of the equivalent rectangular cylindrical metallic tube and the short-circuiting plate is set at ¼ of the wavelength of the subject current to be restricted.

TECHNICAL FIELD

[0001] The present invention relates to a wireless portable device suchas personal data assistant and, more particularly, to a technique forsuppressing electromagnetic coupling between a radio circuit block and adigital circuit block.

TECHNICAL BACKGROUND

[0002] Wireless portable devices such as mobile phone and personaldigital assistant have become popular due to the convenient propertiesthereof, and the thickness and size thereof have been remarkably reducedin these years. FIG. 21A and FIG. 21B are perspective view and sideview, respectively, showing the basic structure of a typical,conventional wireless portable device, and FIG. 21C is an explodedperspective view showing each layer structure of a printed circuit boardtherein. In these figures, a four-layer circuit board is exemplified,wherein a package casing for receiving therein the printed circuit boardis not depicted for simplification purpose.

[0003] The wireless portable device includes an antenna block 20, afeeding block 23, a radio circuit block 21, and a digital circuit block23, which are mounted on the printed circuit board. The antenna bock 20transmits and receives radio waves that are used as signals uponcommunication with a base station etc. The feeding block 23 deliverssignals to the antenna bock 20, and transmits signals supplied throughthe antenna block 20 to the circuit blocks. The radio circuit block 21processes signals that are transmitted or received through the antennablock 20. The digital circuit block 22 processes digital signals thatare used for data processing. Generally, a multi-layered circuit boardhaving multiple layers is used as the printed circuit board 10. Theground layer formed as an internal layer of the printed circuit board 10is used as the common ground for the radio circuit block 21 and digitalcircuit block 22. The printed circuit board used herein includes a firstlayer 11 as a signaling layer, a second layer 12 as the ground layer, athird layer 13 as a power source layer, and a fourth layer 14 as anothersignaling layer, which are disposed in this order as viewed from thefirst layer 11 mounting thereon components. It is to be noted that onlysome of circuit patterns 24 are depicted on the third and fourth layersfor simplification purpose (FIG. 21C). Generally, the spaces betweenthese layers are filled with a dielectric material (not shown) such as aglass epoxy material.

[0004] In the wireless portable device as described above, if there area plurality of transmission channels provided in the same circuit board,and the distance between adjacent transmission channels is short,interaction therebetween may be generated to cause an electromagneticcoupling. An example of the methods which can solve such a problem isdescribed in Patent Publication JP-A-58-092101. In this method,metallized through-halls are provided between the transmission lines,which should be isolated from one another, for connecting together theupper ground conductor and the lower ground conductor, whereby electricisolation is attempted between adjacent transmission lines.

[0005] In Patent Publication JP-A-10-75108, a dielectric waveguide-tubetransmission line is described which is formed by the area encircled bytwo arrayed via-hall groups which electrically connect together theconductor layers. This technique features a subordinary conductor layerformed parallel to the conductor layers and electrically connected tothe via-holes. It is attempted to improve the transmissioncharacteristic therein by introducing such a subordinary conductorlayer. Similar conductor via-halls are used in Patent PublicationJP-A-9-46008. This publication describes the technique wherein thelength of a stub located on the periphery of the ground pattern is madeto be less than ¼ of the wavelength of the high-frequency signaltransmitted through the signal transmission line. The term “stub” asused herein means an edge that is not electrically connected to theground pattern directly. By adopting such a configuration, ahigh-frequency-wave wiring board can be obtained having a reducedinfluence on the high-frequency signals transmitted through the signallines.

[0006] It is to be noted that a structure such as shown in FIGS. 22A and22B may be used for restricting the current flowing on the cable. FIG.22A is a perspective view, and FIG. 22B is a sectional view taken at thecentral plane of the cable. In this configuration, one of the ends of ametallic hollow cylinder 41 is short-circuited by a metallic plate 42,and the metallic hollow cylinder 41 is disposed to cover the cable 43.The length Lc of the hollow cylinder is set at ¼ of the wavelength ofthe current transferred through the tube. In this example depicted, theshort-circuiting plate is connected to the right end to form anelectrically short-circuited plane, whereas the left end constitutes anopen plane. In general, the position apart from the short-circuitedplane by ¼ of the wavelength is an open plane (open end), wherein theinput impedance Zin at the position of the open plane as viewed from theA-side in the drawing assumes a higher value. Accordingly, the current Iflowing from the A-side toward the B-side is suppressed by the effect ofthe higher impedance of the open plane of the structure depicted inthese figures, if it is provided therebetween.

[0007] In general, the frequencies of the signals to be handled aredifferent between the radio circuit block and the digital circuit block.For example, the radio circuit block handles transmitted/receivedsignals having frequencies around 1 GHz (may be around 2 GHz instead,depending on the device). On the other hand, the digital circuit blockhandles a clock signal having a fundamental wave of around 10 GHz, whichgenerates higher-harmonic frequencies equal to the integral multiples ofthe frequency of the fundamental wave. Thus, the ground layer common toboth the circuit blocks receives thereon a mixture of thetransmitted/received signals of around 1 GHz (or around 2 GHz) generatedfrom the radio circuit block and the fundamental-wave and thehigher-harmonic-wave signals generated from the digital circuit block.As a result, there is a tendency that the radio circuit block and thedigital circuit block are susceptible to the influence by theelectromagnetic coupling due to the signals of each other.

[0008] For example, it is probable that the higher-harmonic-wave currentgenerated in the digital circuit block and transferred through theground layer enters a device, such as the IC, in the radio circuitblock. On the other hand, it is also probable that the high-frequencycurrent (radio-frequency-wave current) around 1 GHz generated in theradio circuit block enters the digital circuit block. In the wirelessportable device having reduced size and thickness, it is general thatthe radio circuit blocks and the digital circuit blocks are mixed on asingle circuit board in a closed relationship therebetween. Thus, theelectromagnetic coupling generated between the radio circuit block andthe digital circuit block tends to become more critical. It has beendesired to effectively suppress the electromagnetic coupling between theradio circuit block and the digital circuit block for assuring areliable quality in such a wireless portable device. In the aboveconventional techniques, there is no teaching to effectively solve theproblem while noting the electromagnetic coupling of the signals havingdifferent frequencies between the radio circuit block and the digitalcircuit block.

DISCLOSURE OF THE INVENTION

[0009] The present invention provides a wireless portable device thatcan suppress the electromagnetic coupling between the radio circuitblock and the digital circuit block, by applying the technique shown inFIGS. 22A and 22B to a multi-layer structure of a printed circuit board.More specifically, in the conventional wireless portable device shown inFIG. 22, a metallic plane (a metallic hollow cylinder in the exampleshown in this figure) is configured to enclose the current flowing on atransmission line such as a cable, and the distal end thereof is formedas a short-circuited plane. In addition thereto, by setting the lengthof the metallic plane constituting the transmission line equal to ¼ ofthe wavelength of the current flowing within the tube, the impedance ofthe opening assumes a higher value. This allows restriction of thecurrent flowing from a transmission line connected to the open planeside toward another transmission line connected to the distal end side.In the present invention, a structure equivalently having thisconfiguration is disposed between the digital circuit block and theradio circuit block mounted on the printed circuit board, therebyincreasing the impedance at the position of the open plane. Thisrestricts the current generated from one of the circuit blocks andtransferred through the ground layer from entering the other of thecircuit blocks, thereby suppressing the electromagnetic coupling betweenthe digital circuit block and the radio circuit block.

[0010] In the wireless portable device of the present invention, acurrent restriction structure is provided for suppressing such anelectromagnetic coupling. The current restriction structure is comprisedof a first metallic plane, a second metallic plane and an equivalentmetallic plane implemented by a via-hole array. The first metallic planeis disposed as an overlying layer parallel to the printed circuit boardmounting thereon the radio circuit block and the digital circuit block.The second metallic plate is disposed as an underlying layer parallel tothe printed circuit board. The equivalent metallic plane implemented bythe via-hole array is formed by arranging via-holes on a straight lineat a narrow pitch on the above first and second metallic planes. Such anequivalent metallic plane implemented by the via-hole array is disposedat the position apart from both the ends of each of the first and secondmetallic planes by a distance equal to ¼ of the wavelength of thesubject current to be restricted. Such an equivalent metallic plane actsas a short-circuiting plate for electrically connecting together thefirst and second metallic planes and the ground layer on the printedcircuit board. In addition, equivalent metallic planes are also disposedon both the lateral sides of the first and second metallic planes(although a configuration without them is also possible). Using such aconfiguration, only the upper and lower metallic planes are connectedtogether without connecting the ground layer thereto. By using the aboveconfigurations, a rectangular cylindrical metallic tube is formed whichequivalently encloses therein the ground layer. The subject current tobe restricted is a radio-frequency current generated from the radiocircuit block or a higher-harmonic-wave current generated from thedigital circuit block, or includes both the currents. The rectangularcylindrical metallic tube may have a structure suited to the current tobe restricted. More concretely, the configuration my be such that asingle rectangular cylindrical metallic tube is provided, or such thattwo rectangular metallic plates are provided back to back with theshort-circuiting plate being common thereto.

[0011] As an example of applications of the current restrictionstructure, it is possible to configure the first and second metallicplanes and the equivalent metallic plane to form a □-shape, wherein the□-shape encircles therein the digital circuit block or the radio circuitblock at the center thereof. In such a case, the basic principle is alsosimilar to that as described above. For strengthening the connection orenhancing the function as the short-circuiting plate, a part or whole ofthe via-hole array may be arranged in a plurality of rows. Further, thefirst and second metallic planes may be respectively included in thesignaling layer or the power source layer. The effects of the presentinvention can be obtained so long as the overlying and underlyingmetallic planes are provided to sandwich therebetween the printedcircuit board. Further, even in the case wherein the printed circuitboard is received in a metallic package casing, the current restrictionstructure of the present invention can be applied thereto while assumingthat the package casing is the ground layer of the printed circuitboard.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIGS. 1A and 1B are perspective view and side view, respectively,of a wireless portable device according to a first embodiment of thepresent invention.

[0013]FIG. 2 is an exploded perspective view showing the structure ofeach layer of the printed circuit board of the wireless portable deviceaccording to the first embodiment of the present invention.

[0014]FIGS. 3A and 3B are perspective view and side view, respectively,of the equivalent current restriction structure in the wireless portabledevice according to the first embodiment of the present invention, andFIG. 3C is an exploded perspective view showing the structure of eachlayer of the printed circuit board.

[0015]FIG. 4 shows first and second current restriction structures inthe wireless portable device according to the first embodiment of thepresent invention.

[0016]FIGS. 5A and 5B are perspective view and side view, respectively,of a wireless portable device according to a second embodiment of thepresent invention.

[0017]FIG. 6 is an exploded perspective view showing the structure ofeach layer of the printed circuit board in a wireless portable deviceaccording to a second embodiment of the present invention,

[0018]FIGS. 7A and 7B are perspective view and side view, respectively,of an equivalent current restriction structure in the wireless portabledevice according to the second embodiment of the present invention, andFIG. 7C is an exploded perspective view showing the structure of eachlayer of the printed circuit board.

[0019]FIG. 8 shows first and second current restriction structures inthe wireless portable device according to the second embodiment of thepresent invention.

[0020]FIGS. 9A and 9B are perspective view and side view, respectively,of a wireless portable device according to a third embodiment of thepresent invention.

[0021]FIG. 10 is an exploded perspective view showing the structure ofeach layer of the printed circuit board of the wireless portable deviceaccording to the third embodiment of the present invention.

[0022]FIGS. 11A and 11B are perspective view and side view,respectively, of a wireless portable device according to a fourthembodiment of the present invention.

[0023]FIG. 12 is an exploded perspective view showing the structure ofeach layer of the printed circuit board of the wireless portable deviceaccording to the fourth embodiment of the present invention.

[0024]FIGS. 13A and 13B are perspective view and side view,respectively, of a wireless portable device according to a fifthembodiment of the present invention.

[0025]FIGS. 14A and 14B are perspective view and side view,respectively, of a wireless portable device according to a sixthembodiment of the present invention.

[0026]FIG. 15 is an exploded perspective view showing the structure ofeach layer of the printed circuit board in the wireless portable deviceaccording to the sixth embodiment of the present invention, with thecurrent restriction structure therein shown at the center.

[0027]FIGS. 16A and 16B are perspective view and side view,respectively, of an equivalent current restriction structure in thewireless portable device according to the sixth embodiment of thepresent invention, and FIG. 16C is an exploded view showing thestructure of each layer.

[0028]FIG. 17 shows the first and second □-shaped rectangular currentrestriction structures in the wireless portable device according to thesixth embodiment of the present invention.

[0029]FIG. 18 is a cross-sectional view showing a wireless portabledevice according to a seventh embodiment of the present invention.

[0030]FIGS. 19A and 19B are perspective view and side view,respectively, of a wireless portable device according to an eighthembodiment of the present invention.

[0031]FIGS. 20A and 20B are perspective view and side view,respectively, of a wireless portable device according to a ninthembodiment of the present invention.

[0032]FIGS. 21A and 21B are perspective view and side view,respectively, of a typical wireless portable device of a prior art, andFIG. 21C is an exploded view showing the structure of each layer of theprinted circuit board.

[0033]FIGS. 22A and 22B are respectively a perspective view of thestructure restricting the current on a typical cable in the prior artand a sectional view taken on the central plane of the cable.

BEST MODES FOR CARRYING OUT THE INVENTION

[0034] Embodiments of the wireless portable device according to thepresent invention will be described in detail with reference to thedrawings. Each printed circuit board shown herein is a four-layercircuit board (first layer/signaling layer; second layer/ground layer;third layer/power source layer; and fourth layer/signaling layer),similarly to the structure of the conventional device. The space betweenadjacent layers of the circuit board is filled with a dielectricmaterial such as a glass epoxy material etc., although not specificallydepicted. The via 25 hole used herein is such that a conductive layer isformed around an air hole. The via-hole penetrating a metallic patternis thereby connected to the metallic pattern. It is to be noted thataligned positions of the layers at which a via-hole penetrates areprovided with holes to be used for the via-holes.

[0035] Referring to FIGS. 1A, 1B and 2 showing a first embodiment of thepresent invention, the wireless portable device of the presentembodiment has a configuration wherein, for isolation of a radio circuitblock 21 from a digital circuit block 22, a current restrictionstructure 1 is mounted between both the circuit blocks disposed in aprinted circuit board. The current restriction structure 1 includesmetallic planes 2 and 3 disposed parallel to the overlying andunderlying layers (first layer and third layer) so as to sandwichtherebetween the ground layer. Arrays of via-holes 5 are formed toextend along straight lines on both lateral sides of the metallic planes(the locations of the metallic planes roughly corresponding to the endsof the printed circuit board as viewed in the direction normal to thedirection connecting together the radio circuit block and the digitalcircuit block), and formed at a location which is apart by desireddistances (Lr and Ld) from both the ends of the metallic planes asviewed in the direction connecting together the radio circuit block andthe digital circuit block.

[0036] The ground layer 4 is configured to have a width somewhat smallerthan the width of a portion of the metallic planes sandwiched betweenthe via-hole arrays. Accordingly, the width of this portion of themetallic planes is somewhat larger than the width of the ground layer.The overlying metallic plane 2 and the underlying metallic plane 3 havethe same dimensions, wherein the length thereof as viewed in thedirection connecting together the radio circuit block and the digitalcircuit block is L (=Lr+Ld), and the width in the direction normalthereto is same as the width of the circuit board. Each of thesemetallic planes is obtained by combining two metallic strips (a metallicstrip having a length of Lr and located on the side of radio circuitblock, and another metallic strip having a length of Ld and located onthe side of the digital circuit block) at the via-hole array as theboundary therebetween, as will be described later.

[0037] The lengths of Lr and LdB of the metallic strips are set at ¼ ofthe wavelengths of the subject current to be restricted. For example,assuming that fr is the frequency of the radio-frequency current(corresponding to a wavelength of λr) to be restricted from entering thedigital circuit block out of the radio circuit block, and that fd is thefrequency of the higher-harmonic-wave current (corresponding to awavelength of λd) to be restricted from entering the radio circuit blockout of the digital circuit block, the Lr and Ld are expressed by thefollowing equations:

Lr=λr/4=(c ₀ /fr)/4  (1), and

Ld=λd/4=(c₀ /fd)/4  (2),

[0038] wherein co is the velocity of light (3×10⁸ m/s).

[0039] As depicted, the via-holes penetrate from the first layer to thethird layer, wherein the via-holes disposed Lr apart from one end of themetallic planes (disposed Ld apart from the other end) electricallyconnect together the overlying and underlying metallic planes and theground layer. In addition, the via-holes disposed on both lateral sidesof the metallic planes electrically connect together the overlying andunderlying metallic planes (without connecting to the ground layer).That the via-holes disposed on both lateral sides of the metallic planedo not connect the ground layer results from the fact that the width ofthe metallic planes is larger than the ground width at the position andthus the via-holes penetrate the printed circuit board withoutpenetrating the ground layer.

[0040] In the present invention, the spacing between the adjacentvia-holes is significantly shorter than the wavelength to be considered,whereby the via-holes are disposed at a narrow pitch or at a highdensity. This allows the via-hole array to be construed as an equivalentmetallic plate. In consideration of this fact, the current restrictionstructure 1 can be equivalently expressed by the structure of arectangular cylindrical metallic tube shown in FIG. 3, wherein only thecurrent restriction structure is depicted. The via-hole array located onboth the lateral sides of the metallic planes is equivalently expressedby metallic strips 7 (7 a/7 b) and 8 (8 a/8 b) which couple together theoverlying and underlying metallic planes. Thus, the configuration isequivalently such that the ground layer is completely enclosed withinthe four metallic planes (overlying metallic plane 2, underlyingmetallic plane 3, and both the side metallic planes 7 and 8). In otherwords, the configuration is such that the ground layer is covered by arectangular cylindrical metallic tube. The via-hole array which is Lrapart from one end of the metallic plane (and at the same time, Ld apartfrom the other end) is equivalently expressed by a short-circuitingplate 6 (6 a and 6 b) which connects together the overlying andunderlying metallic planes and the ground layer.

[0041] As understood from FIGS. 1A, 1B, 2, and 3A to 3C, such aconfiguration can be construed as two current restriction units (tworectangular cylindrical metallic tubes) juxtaposed with each other, withthe via-hole array (short-circuiting plate 6) having the configurationas described above being the boundary. More specifically, as shown inFIG. 4, the configuration can be construed such that the first currentrestriction unit 1 a is disposed on the radio circuit block side,whereas the second current restriction unit 1 b is disposed on thedigital circuit block side, with the short-circuiting plates 6configured as the via-hole array being disposed back to back.

[0042] The first current restriction unit 1 a has a configurationwherein the distal end thereof as viewed from the radio circuit block isshort-circuited. The metallic strips formed as the overlying, underlyingand side layers for the ground layer have a length (Lr) equal to ¼ ofthe wavelength, λr, of the subject radio-frequency current in thedirection connecting together the radio circuit block and the digitalcircuit block. In this manner, the current restriction unit has aconfiguration wherein a transmission line (having a shortcircuiteddistal end) is formed to enclose therein a ground layer, and thetransmission line has a length of λr/4. Thus, the input impedanceagainst the radio circuit block is higher at the position of the openplane of the first current restriction unit 1 a. The effect of thishigher impedance is that the radio-frequency current generated from theradio circuit block and transferring through the ground layer isprevented from flowing toward the digital circuit block, whereby theelectromagnetic coupling can be suppressed. On the other hand, thesecond current restriction unit 1 b has a configuration wherein thedistal end thereof as viewed from the digital circuit block isshortcircuited. The metallic strips formed as the overlying, underlyingand side layers for the ground layer have a length (Ld) equal to ¼ ofthe wavelength, λd, of the subject higher-harmonic-wave current in thedirection connecting together the radio circuit block and the digitalcircuit block. Thus, also in this case, the input impedance against thedigital circuit block is higher at the position of the open plane of thesecond current restriction unit 1 b. The effect of this higher impedanceis that the higher-harmonic-wave current generated from the digitalcircuit block and transferring through the ground layer is preventedfrom flowing toward the radio circuit block whereby the electromagneticcoupling can be suppressed.

[0043] As described above, in the wireless portable device of thepresent embodiment, the effect of the current restriction structure isthat the higher-harmonic-wave current is restricted from entering theradio circuit block out of the digital circuit block, and theradio-frequency current is restricted from entering the digital circuitblock out of the radio circuit block. This suppresses theelectromagnetic coupling between the radio circuit block and the digitalcircuit block, thereby assuring a more excellent quality for thewireless portable device.

[0044] Referring to FIGS. 5A, 5B and 6 showing a second embodiment ofthe present invention, the wireless portable device of the presentembodiment is such that only via-hole arrays disposed on both lateralsides of the metallic planes in the wireless portable device of thefirst embodiment are removed. Also in this case, the width of the groundlayer is equivalent to that of the circuit board, wherein the via-holearrays are arranged at a narrow pitch and a high density to penetratethe first through third layers. Thus, the via-hole array can beconstrued equivalently as a metallic plate without problem, wherein thecurrent restriction structure 1 can be equivalently expressed by thestructure shown in FIG. 7. In this case, the current restrictionstructure 1 is such that the first current restriction unit 1 a ismounted on the side at which the radio circuit block is disposed and thesecond current restriction unit 1 b is mounted on the side at which thedigital circuit block is disposed, with the short-circuiting plates 6formed by the via-hole array being disposed back to back.

[0045] In the present embodiment, the principle is same as that of thefirst embodiment, although there is no metallic strip disposed on boththe lateral sides (it is not a “tube” in a strict meaning; however, mayconstitute a rectangular cylindrical metallic tube in principle). Morespecifically, due to a higher input impedances at the respective openplanes of the first and second current restriction units having lengthsof λr/4 and λd/4, respectively, measured from the short-circuiting plate6, the current generated from one of the circuit blocks is preventedfrom flowing to the other of the circuit blocks. Thus, theelectromagnetic coupling can be suppressed similarly to the firstembodiment.

[0046] In the first and second embodiments, there are shown wirelessportable devices capable of suppressing the electromagnetic couplingbetween the radio circuit block and the digital circuit block.

[0047] Referring to FIGS. 9A, 9B and 10 showing a third embodiment ofthe present invention, in a wireless portable device of the presentembodiment, only a higher-harmonic-wave current entering the radiocircuit block from the digital circuit block is noticed, and isrestricted. These figures show a wireless portable device mountingthereon a current restriction structure for restricting thehigher-harmonic-wave current from entering the radio circuit block outof the digital circuit block. The present embodiment has a configurationwherein only the second current restriction unit of the first embodimentis mounted, a single equivalent rectangular cylindrical metallic tube isprovided, and a U-shape via-hole array is formed.

[0048] Similarly, as a configuration of a fourth embodiment of thepresent invention, the wireless portable device may mount thereon acurrent restriction structure for restricting the radio-frequencycurrent from entering the digital circuit block out of the radio circuitblock (FIGS. 11A, 11B and 12). The present embodiment has aconfiguration wherein only the first current restriction unit of thefirst embodiment is mounted, a single equivalent rectangular cylindricalmetallic tube is provided, and a U-shape via-hole array is formed. Thethird and fourth embodiments have similar advantages for suppressing theelectromagnetic coupling (in one direction).

[0049] In the embodiments described heretofore, the via-hole arraydescribed therein has a single row. Referring to FIGS. 13A and 13Bshowing a fifth embodiment of the present invention, the wirelessportable device of the present embodiment has a configuration whereinthe via-hole array used in the second embodiment, for example, isarranged at a narrow pitch, in a cyclic manner and in a plurality ofrows. Such a configuration allows enforcement of the connection of theoverlying metallic plane 2, underlying metallic plane 3 and the groundlayer 4 (physical enforcement of the connection). In addition, since aplurality of metallic plates are equivalently disposed therein, thefunction of the short-circuiting plate is more effective. Further, eachof the via-hole arrays disposed on the lateral sides of the metallicplanes may be arranged at a narrow pitch, in a cyclic manner, and in aplurality of rows. In this case, the connection between the metallicplane 2 overlying the ground layer and the metallic plane 3 underlyingthe ground layer can be enforced. In this way, each of some or all ofthe via-hole arrays may be arranged in a plurality of rows. As shown inFIG. 13, one of the outermost rows among a plurality of rows of thevia-hole array is disposed on the location of the metallic plane apartfrom the end thereof in the direction of a line passing through theradio circuit block and the digital circuit block by ¼ of the wavelengthof the subject current to be restricted. Thus, the length of themetallic plane is increased in the direction by the width of theplurality of rows of the via-hole array. Such a configuration whereinthe via-hole array has a plurality of rows can be also employed in theembodiments to follow.

[0050] Referring to FIGS. 14A, 14B and 15 showing a sixth embodiment ofthe present invention, the digital circuit block is disposed in thevicinity of the center of the printed circuit board for the sake ofconvenience. More concretely, the wireless portable device of thepresent embodiment has a configuration wherein a □-shaped currentrestriction structure 34 is mounted on the circumference of the digitalcircuit block. This corresponds to the configuration wherein the currentrestriction structure 1 described in connection with the first throughfifth embodiments is disposed to encircle the digital circuit block 22,and the basic structures thereof such as the film structure are similarto those of those embodiments.

[0051] In the present embodiment, the □-shaped metallic planes(overlying metallic plane 32 and underlying metallic plane 33) aredisposed parallel to the overlying and underlying layers (first layerand third layer) to sandwich therebetween the ground layer. Each of themetallic planes is configured to a pattern having therein an opening,which is somewhat larger than the size of the periphery of the digitalcircuit block, and having a widthwise length of Lr+Ld as in the cases ofthe above embodiments. The via-hole array is disposed apart from theinner edge of the metallic plane by a desired distance (Ld) to form a□-shape, wherein individual via-holes penetrate from the first layer tothe third layer. The overlying and underlying metallic planes and theground layer are connected together at the locations at which thevia-holes reside, and the spacing of adjacent via-holes is considerablysmaller than the wavelength to be considered and thus adapted to anarrow pitch and high density mounting. Thus, the via-hole array can beconstrued as a metallic plate also in this case. The □-shaped via-holearray is located at a distance of Ld apart from the inner edge of themetallic plane and at a distanced of Lr apart from the outer edgethereof, whereby these lengths are set at ¼ of the wavelengths of thesubject currents to be restricted.

[0052]FIGS. 16A to 16C and 17 show the □-shaped current restrictionstructure 34 wherein the via-hole array is equivalently construed as ametallic plate. FIG. 17 illustrates the □-shaped first and secondcurrent restriction units in the present embodiment. As shown in thesefigures, this can be construed as a structure of two lopped currentrestriction units mounted, wherein the □-shaped short-circuiting plates31 (31 a and 31 b) implemented by the via-hole array are disposed backto back. The first □-shaped current restriction unit 34 a is mounted onthe inner side (the side at which the digital circuit block is mounted)of the via-hole array constituting a boundary, and is implemented by□-shaped metallic planes (32 and 33) each having a short-circuiteddistal end and a widthwise length, Ld, equal to ¼ of the wavelength λdof the subject higher-harmonic-wave current. The □-shaped second currentrestriction unit 34 b is mounted on the outer side, and is implementedby □-shaped metallic planes (32 and 33) each having a short-circuiteddistal end and a widthwise length, Lr, equal to ¼ of the wavelength λrof the subject radio-frequency current. Thus, the □-shaped first currentrestriction unit 34 a, as disposed to surround the digital circuit block22 and having a higher impedance at the open plane directed inwardly,can suppress the higher-harmonic-wave current from flowing out of thedigital circuit block to the circumference thereof. As a result,entering of the higher-harmonic-wave current to the radio circuit block,for example, can be restricted, thereby suppressing the electromagneticcoupling. Similarly, the □-shaped second current restriction unit 34 bhas an open plane directed outwardly. Accordingly, entering of thecurrent to the digital circuit block from nearby circuit blocks etc. isrestricted, thereby suppressing the electromagnetic coupling. In thepresent embodiment, although the shape of the current restrictionstructure is inadequate to be referred to as “tube”, the advantage ofthe rectangular cylindrical metallic tube in the present embodiment isbasically similar to those of the above embodiments.

[0053] In the above first through fifth embodiments, the currentrestriction units are disposed between the circuit blocks which is mayinvolve an electromagnetic coupling therebetween, having an effect onthe current flowing into the ground layer of the printed circuit board.On the other hand, in the present embodiment, the □-shaped currentrestriction structure is disposed to surround the location at which thecurrent is generated (the circuit block surrounded may be either adigital circuit block as in the present embodiment or a radio circuitblock). Thus, the present embodiment has the advantage of restrictingthe current, which may possibly cause the electromagnetic coupling, fromflowing onto the printed circuit board. It is to be noted that a printedcircuit board may have eight layers or sixteen layers, for example,other than the four layers in the wireless portable device of thepresent invention, although the four-layer circuit boards areexemplified heretofore. In addition, although the metallic planes (2 and3) formed to overlie and underlie the ground layer are included in thesignaling layer and the power source layer (first layer and thirdlayer), respectively, independent layers having the metallic planes maybe provided separately from these layers. Or else, it is possible toemploy a configuration wherein either one of the overlying andunderlying metallic planes is included in the signaling layer or thepower source layer.

[0054] In the embodiments to follow, modifications from the aboveembodiments will be exemplified. The advantages of the present inventionin the modifications are also similar to those in the above embodiments.Referring to FIG. 18 showing a seventh embodiment of the presentinvention, the overlying and underlying metallic planes are formedrespectively on first layers, when numbered from the ground layer, inthe wireless portable device of the present embodiment; however, thelayers having the metallic planes may be disposed in any of the layersso long as these layers overlie and underlie the ground layer. Forexample, in the case of N-layer circuit board shown in FIG. 18, theoverlying metallic plane may be formed on the (N-3)-th layer and theunderlying metallic plane may be formed on the N-th layer, assuming thatthe ground layer resides on the (N-1)-th layer etc.

[0055] It is to be noted that some of the package casings for thewireless portable devices may be made of a metallic material, althoughmost of them are made of a nonmetallic material such as plastics orresin. In such a case, a current which may possibly cause theelectromagnetic coupling may flow on the surface of the package casing.For suppressing the electromagnetic coupling caused by such a current,as shown in FIG. 19, the current restriction structure of the presentinvention may be applied to the casing 52, assuming that the metallicpackage casing 52 is an equivalent ground layer. This structure may besuch that the rectangular cylindrical metallic tube covers the metallicpackage casing for substantially complete enclosure thereof, and ashort-circuiting plate is connected thereto for short-circuitingtogether the metallic package casing and the rectangular cylindricaltube at the position Lr apart from one end of the rectangularcylindrical metallic tube (or Ld apart from the other end thereof). Aswill be understood from the same figure, this configuration correspondsto the configuration wherein the current restriction structureimplemented by the metallic plate shown in FIG. 3 is applied to themetallic package casing 52. In this figure, only the ground layer shownin FIG. 3 is replaced by the metallic package casing 52. Accordingly,the advantage is similar to those in the embodiments describedheretofore, whereby the electromagnetic coupling caused by the currenton the package casing can be suppressed.

[0056] Referring to FIG. 20 showing a ninth embodiment of the presentinvention, the wireless portable device of the present embodiment issuch that the current restriction structure in the second embodiment isapplied to a metallic package casing for the case using the metallicpackage casing 52 as well. Also in this case, only the ground layer isreplaced by the metallic package casing. Thus, the advantage is similarto those in the embodiments described heretofore. Essentially, thelength of the metallic strip of the current restriction structure isequal to ¼ of the wavelength of the subject current. In the presentembodiment, a magnetic member 50 (or an insulator member 50) is embeddedbetween the ground layer and the metallic plane, thereby intending toreduce the size of the metallic plane to take advantage of thewavelength reduction effect (FIG. 20). It is to be noted that thepresent invention is not limited to application to the wireless portabledevice such as portable cellular phone and personal data assistant, andmay be applied to general electronic or electric appliances. Forexample, in an electronic or electric appliance, a magnetic coupling mayoccur between a digital circuit block and an analog circuit block(corresponding to the radio circuit block in the present invention). Thepresent invention, if applied to such a case, has a similar advantage.

[0057] As described above, in the wireless portable device of eachembodiment of the present invention, since the current restrictionstructure restricts the higher-harmonic-wave current from entering theradio circuit block out of the digital circuit block, and theradio-frequency current from entering the digital circuit block out ofthe radio circuit block, the electromagnetic coupling between thedigital circuit block and the radio circuit block can be suppressed toassure a higher quality.

1. A wireless portable device comprising, on a single printed circuitboard, a radio circuit block for processing signals received/transmittedfrom/to a base station and a digital circuit block for processingdigital signals in data processing, characterized by: a currentrestriction structure disposed between said radio circuit block and saiddigital circuit block, wherein: said current restriction structurerestricts a radio-frequency current generated in said radio circuitblock and transferred through said ground layer of said printed circuitboard from entering said digital circuit block, and/or ahigher-harmonic-wave current generated in said digital circuit block andtransferred trough said ground layer of said printed circuit board fromentering said radio circuit block.
 2. A wireless portable devicecomprising, on a single printed circuit board, a radio circuit block forprocessing signals received/transmitted from/to a base station and adigital circuit block for processing digital signals in data processing,characterized by: a current restriction structure disposed between bothsaid circuit blocks, wherein: said current restriction structure isimplemented by one or two of equivalent rectangular cylindrical metallictube for restricting a subject current to be restricted, which is eitherof a radio-frequency current generated in said radio circuit block and ahigher-harmonic-wave current generated in said digital circuit block,from transferring out of one of said current blocks to the other of saidcurrent blocks via said ground layer on said printed circuit board; andsaid rectangular cylindrical metallic tube is implemented by metallicplanes and a via-hole array which are configured to enclose said subjectcurrent and have a short-circuiting plate at a distal end thereof, and adistance between an open plane of said rectangular cylindrical metallictube opposing one of said both circuit blocks and said short-circuitingplate is set at ¼ of a wavelength of said subject current, to therebyobtain a higher impedance at said open plane to restrict said entering.3. The wireless portable device according to claim 2, wherein: saidcurrent restriction structure includes a first current restriction unitconfigured as an equivalent rectangular cylindrical metallic tube forrestricting said radio-frequency current generated in said radio circuitblock, and a second current restriction unit configured as anotherequivalent rectangular cylindrical metallic tube for restricting saidhigher-harmonic-wave current generated in said digital circuit bloc; andsaid first current restriction unit and said second current restrictionunit are coupled together back to back so that said short-circuitingplates connected to said distal ends of said first current restrictionunit and said second current restriction unit are common.
 4. Thewireless portable device according to claim 2, wherein said currentrestriction structure includes either one of a first current restrictionunit implemented by an equivalent rectangular cylindrical metallic tubefor restricting said radio-frequency current generated in said radiocircuit block, and a second current restriction unit implemented byanother equivalent rectangular cylindrical metallic tube for restrictingsaid higher-harmonic-wave current generated in said digital circuitblock.
 5. A wireless portable device comprising, on a single printedcircuit board, a radio circuit block for processing signalsreceived/transmitted from/to a base station and a digital circuit blockfor processing digital signals in data processing, characterized by: acurrent restriction structure disposed between both said circuit blocksfor restricting a subject current to be restricted, which is either aradio-frequency current generated in said radio circuit block or ahigher-harmonic-wave current generated in said digital circuit block,from entering one of said circuit blocks out of the other of saidcircuit blocks via a ground layer of said printed circuit board,wherein: said current restriction structure includes a first metallicplane overlying and parallel to said printed circuit board, a secondmetallic plane underlying and parallel to said printed circuit board,and equivalent metallic plane implemented by a via-hole array.
 6. Thewireless portable device according to claim 5, wherein: said firstmetallic plane and second metallic plane have a length set at a sum(Lr+Ld) of a length Lr equal to ¼ of a wavelength of saidradio-frequency current and a length Ld equal to ¼ of a wavelength ofsaid higher-harmonic-wave current, in the direction connecting ends ofsaid both circuit blocks together, and a width set equal to a width ofsaid printed circuit board, in a direction normal to the directionconnecting said ends of both said circuit blocks together; and saidequivalent metallic plane implemented by said via-hole array is formedby arranging via-holes linearly at a narrow pitch at a location of saidfirst and second metallic planes, which is Lr apart from an end of saidradio circuit block and Ld apart from an end of said digital circuitblock, said via-holes penetrating through a ground layer of said printedcircuit board.
 7. The wireless portable device according to claim 5,wherein: said first metallic plane and second metallic plane have alength set at a sum (Lr+Ld) of a length Lr equal to ¼ of a wavelength ofsaid radio-frequency current and a length Ld equal to ¼ of a wavelengthof said higher-harmonic-wave current, in the direction connecting endsof said both circuit blocks together, and a width set larger than awidth of said ground layer of said printed circuit board in a directionnormal to the direction connecting said ends of said both circuit blockstogether; said equivalent metallic plane implemented by said via-holearray is formed by arranging via-holes linearly at a narrow pitch at alocation of said first and second metallic planes, which is Lr apartfrom an end of said radio circuit block and Ld apart from an end of saiddigital circuit block, said via-holes penetrating through said groundlayer of said printed circuit board, and by arranging other via-holeslinearly at a narrow pitch at locations of said first and secondmetallic planes, which are substantially aligned with both ends of saidprinted circuit board in a direction normal to said direction connectingsaid ends of said both circuit blocks together, said other via-holespenetrating locations of said printed circuit board other than alocation of said ground layer.
 8. The wireless portable device accordingto claim 5, wherein: said current restriction structure is configured torestrict either one of said subject currents; said first metallic planeand said second metallic plane have a length equal to ¼ of a wavelengthof said either one of said subject currents in a direction connectingends of both said circuit blocks together; said equivalent metallicplane implemented by said via-hole array is configured to form a U-shapeby arranging via-holes linearly at a narrow pitch and at ends of saidfirst and second metallic planes far from one of both said circuitblocks generating said either one of said subject currents to penetratesaid printed circuit board at said ground layer, and by arranging othervia-holes linearly at a narrow pitch at locations of said fist andsecond metallic planes, which are substantially aligned with both endsof said printed circuit board in a direction normal to said directionconnecting said ends of said both circuit blocks together to penetratelocations of said printed circuit board other than a location of saidground layer.
 9. The wireless portable device according to claim 5,wherein said first metallic plane and said second metallic plane are ofa □-shape having an opening therein somewhat larger than a size of aperiphery of either one of both said circuit blocks, and having a widthequal to a sum (Lr+Ld) of a length Lr equal to ¼ of a wavelength of saidradio-frequency current and a length Ld equal to ¼ of a wavelength ofsaid higher-harmonic-wave current, and are disposed as overlying andunderlying layers parallel to said printed circuit board so as tosurround said either one of both said circuit blocks; and via-holes arearranged at a narrow pitch and at a location of said shaped first andsecond metallic planes which is apart from an inner edge thereof by ¼ ofa wavelength of said subject current generated by said either one ofboth said circuit blocks, said via-holes penetrating said ground layerof said printed circuit board.
 10. The wireless portable deviceaccording to any one of claims 6 to 9, wherein: a part or whole of saidequivalent metallic plane implemented by said via-hole array isconfigured by a plurality of rows of via-holes arranged on said firstand second metallic planes at a narrow pitch; and for arranging saidvia-hole array at the location of said first and second metallic planeswhich is apart from one end or both ends thereof by ¼ of said wavelengthof said subject current, a distance between said one end or both endsand an outermost row of said via-hole array among said plurality of rowsis set at ¼ of the wavelength of said subject current, and the length ofsaid first and second metallic planes is increased by the width of saidplurality of rows.
 11. The wireless portable device according to any oneof claims 6 to 10, wherein, for the case wherein said printed circuitboard is sandwiched between an overlying printed circuit board and anunderlying printed circuit board to form a multi-layer printed circuitboard; one or both of said fist and second metallic planes is includedin either one or both of a signaling layer and a power source layerprovided in said multi-layer printed circuit boards.
 12. The wirelessprinted circuit board according to any one of claims 6 to 11, wherein,for the case wherein said printed circuit board is received in ametallic package casing, said current restriction structure is appliedthereto while construing said metallic package casing as said groundlayer of said printed circuit board.
 13. The wireless printed circuitboard according to claim 12, wherein a material having a wavelengthreduction effect for the current is provided between said package casingand said current restriction structure.